The effect of chronic morphine administration will be determined on regional brain acetylocholine content in the rat. Six major regions of the rat brain will be studied including the cerebral cortex, mesencephalon, thalamus, hypothalamus, striatum and hippocampus. Content and turnover of acetylcholine will be measured using GC-MS techniques. Morphine will be given chronically tid for 14 days. Morphine pellet implanted animals will also be studied 3 days after pellet implantation. Natural, abrupt and naloxone induced morphine withdrawal will be compared. The purpose of this research is to clarify the role of brain acetylcholine, particularly its turnover in narcotic dependence and withdrawal. BIBLIOGRAPHIC REFERENCES: Domino, E.F., Vasko, M., and Wilson, A.E.: Mixed depressant and stimulant actions of morphine and their relationship to brain acetylcholine. Accepted by Life Sciences 1975. Domino, E.F., Vasko, M.R. and Wilson, A.E.: Biphasic actions of selected narcotics on rat locomotor activity and brain acetylcholine utilization. In Tissue Responses to Addictive Drugs ISPNE Workshop, ed. by D.H. Ford and D. Clouet, Raven Press, New York, In press, 1975.